How to fix my phone when everything seems ok except for the charging.?

Hello,

I dropped my phone the other day. I just got this phone on august 2021. When it dropped, it drop flat on the floor. I checked the camera, touchscreen and screen. Everything looks good. No cracks or anything. However, when i tried to charge it last night using fast charger wired, it was charging too slow. I charged it when it was at 14% but after 30 mins, it was only at 19%. I then tried wireless and it seems a little faster? But still very slow compared to before. Now i just remove the case of the phone and shook it. I hear something when it gets shaken. How do i open the back of the phone? Im guessing something got loose?